Credit Card Validation Algorithm | Dataford Interview Questions

Validate a credit card number (similar to HackerRank "Validating Credit Card Numbers"); write the optimal approach on paper and explain time complexity.

Asked in the Onsite round 1 stage. Candidate says the asked problem was slightly similar to the HackerRank problem. Reported follow-ups: How would you generalize the code for other applications? How would the application work in real time?

Contract

Implement def validate_card_number(card_number):. The input is a string containing 13 to 19 digits, optionally separated by consistent single spaces or hyphens. Return True when formatting is valid and the digits satisfy the Luhn checksum; otherwise return False.

Constraints

card_number is a string.
The normalized number contains 13 to 19 digits.
Separators are optional, but if present they are single consistent spaces or hyphens.
Separators cannot be leading, trailing, consecutive, or mixed.

Function Signature

def validate_card_number(card_number):

Your question is Credit Card Validation Algorithm. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.

Problem